#include<iostream>
using namespace std;
int main(){
	
	int n,f[1001];
	f[1] = 1;
	f[2] = 1;
	cin >> n;
	for(int i = 3; i < 1001; i++){
		f[i] = f[i - 1] + f[i - 2];
	}
	cout << f[n] << endl;
	return 0;
}
